William s



UNITED STATES PATENT OFFICE.

, WILLIAM s. HUDSON, or PATEEsoN, NEW JEEsEY.

IMPROVED DEVICE FOR OPERATING SAFETY-VALVES.

Specification forming part of Letters Patent No. 46,238, dated February 7,1865.

To all whom t may concern:

Be it known that I, WILLIAM S. HUDSON, of Paterson1 in the county of Passaic and State of New Jersey, have invented a certain new and useful Improvement in theMeans for Operatin g Safety-Valves; and I do hereby declare that the following is a full and exact description thereof.

The accompanying drawings form a part of this specification.

Figure lis aplan View, and Fig. 2 a side elevation.

rEhe figures show the parts containing the novelty, with so much ofthe other parts as are necessary to indicate their relation thereto.

Similar letters of reference indicate like parts in both the gures. Tints are employed to aid in distinguishing parts, and do not imply a difference in material. The material of the whole may be iron or steel.

My invention tends to reduce the probabilities ot' excessive pressure in a boiler. Itis well known that safety-valves, when held down by the action of springs, do not perform in practice with the perfection theoretically ascribed to them, because when steam is generated rapidly, so that a large quantity must be discharged through the safety-valve, the safety-valve cannot rise sufliciently from its seat without chan ging the relation of the spring thereto. In other words, a safety-valve loaded :y a spring, so as to lift at a given pressure when it rises to a considerable height from its seat, either experiences a greater resistance from the spring, and consequently calls for a still higher pressure of steam to hod it at that height, or there mustbe some peculiar provision for adapting it to this emergency.

Several inventions have been made for connecting the spring to the valve through the aid of bell-crank levers or other analogous devices so arranged that the leverage of the spring shall diminish as the valve rises. It is obvious that such arrangement may be carried to such an extent that the pressure required to sustain the valve at a suitable height above its seat, instead of being greater shall be actually less than that required to first start it from its seat. l employ such devices in my invention in combination with another device that recently patened to (lharlesGraham, patent dated v18th December, 1860.

My inventionis very simple and effectiveand possesses very marked advantages, particularly on locomotives. By its means the engineer may leave his engine in a tolerably safe condition, either with or without taking the precaution necessary with devices heretofore used. It is safer, and generally better, for obvious reasons, for the engineer to shift the handle before dismounting, especially if the fire is very intense and he expects to beabsent any considerable period. In such case the safety-valve, which is ordinarily loaded to a pressure of, say, one hundredand ten pounds per square inch, will commence to blow oli at one hundred or some other lower pressure, according as the device is constructed; but in case he should, through forgetfulness or other cause, dismount without such precaution, the safety-valve retains its seat, holding the boiler tight until the pressure of one hundred and ten pounds is reached. lt will then relieve the boiler eft'ectually, and will rise higher and higher to discharge great volumes of steam without accumulating any increased tension in the boiler.

To enable others skilled in the art to make and use my invention, I will proceed to describe its construction and operation by the aid of the drawings and of the letters of reference marked thereon.

A, Fig. 2, is one of the threaded rods which descends from the ends of the ordinary safetyvalve lever. (Not represented.) It will be understood that the two safety-valves act on said levers in the ordinary manner, so as to lift each of the rods A with a force corresponding to the pressure of the steam.

B- is a right andleft hand nut, and B an ordinary'jam-nut.

C is a threaded rod, crooked as represented, and adapted to fit the lower part of the right and left nut, B.

D is the lower, and D2 the upper arm of a bell-crank lever which is mounted on the fulcrum or shaft D, which is mounted in fixed centers, as represented.

There are two'of the bell-crank levers D D2, each mounted loosely on the shaft D, so that they m ay turn independently of each other to any extent required, and there are two safetyvalves and safety-valve levers mounted independently, but near each other. The lever of each is held down by a rod, A C. There are, therefore, two of the rods A C.

The remaining parts to be described arel represented in both drawings and involve the novelty ot my invention.

E E are crooked links depending from the ends of the upper arms, D2, of the bell crank lever before described. The lower ends of the links E are connected to the levers G. These latter levers turn on iixed centers or fulcra and transmit a powerfullifting force to the knife-edged cross-bar H H. The latter carries one end of the half-elliptic spring I. This spring is held down at its center by a suitable cross-bar, J, which may be adjusted at different hights, if necessary, by turning the nuts 7c on the bolts K. It is not intended to change the position of this cross-bar J after the apparatus has been properly constructed and adjusted, unless the tension of the spring should become changed, or it should become desirable to change the point at which the steam shall commence to blow oif.

The forward end of the half-elliptic spring I, or that end thereof which is farthest removed from the bar H, rests on a shaft, L, which is adapted to turn on bearings L', which are eccentric to the aXis ofthe shaft L. These are mounted in iixedsupports, as indicated. By turning the eccentric shaft L by means of the handle M, which is Iixed thereto, the corresponding` end of the half-elliptic spring I is raised or lowered at pleasure by the eccentric motion of the shaft L. The lever M is conveniently accessible to the engineer, so that he can at pleasure turn it down or up, and the spring I is notched, as indicated at t', to allow the lever to be lifted.' When it is turned up out of the way, which is the ordinary condition under which the locomotive will work,the spring I is exercising its full proper tension, pressing down on the knife-edged cross-bar H, and consequently pressing downward the levers Gr G, and the connecting-links E and both arms D D2 of the bell-crank levers. It consequently holds down the two rods (l A and the two connected main levers and safetyvalves. (Not represented.)

When the end of the handle or lever M is pulled down and left in the position represented, or still lower, the forward end of the half-elliptic spring I is allowed to yield downward by reason of the eccentricity of the shaft L, and, as the cross-bar J remains stationary, the tension of the spring I 011 the cross-bar H and the whole connected train referred to is lessened, so that the steam may lift the saft-yposition, it will rise. Now, the slightest vertical movement of the rod A C changes the leverage of the half-elliptic spring I by the change of the position of the two arms D D2 of each of the bellcrank levers. In otherwords, so soon as the safety-valves commence to rise and to deliver the steam', the act of rising by turning the bell-crank levers slightly on their center D causes the arm D to assume a more nearly horizontal position and the arms D2 to assume a more nearly perpendicular position. The consequence of this change will be readily recognized. The leverage at which the steam acts on the arms D' is increased by the change of position, and-the leverage by which the spring I acts on the arms D2 is decreased by said change. Consequently, the

pressure which is suiicient to commence to lift the safetyfvalves'will easily lift them to such height, by reason of this increased leverage, that any possible quantity ofsteam which can be generated in a given unit of time in t1e boiler will be delivered through the safetyvalve without accumulating an increased pressure in the boiler. This'result will obtain whatever may be the pressure at which the steam commences to lift the safety-valves.

N is a spring which presses upward against the under side lof the eccentric shaft L. lt serves to partially balance the l1andlever M, and thus to aid in sustaining it in any position desired, and by its friction prevents the lever from moving too readily.

Having now fully described my invention, what l claim as new in safety-valve arrangements, and desire to secure by `Letters Pattent, is-

The bell crank levers, in combination with the means L M, or 'their equivalents, for rapidly changing the initial tension of the spring l within Wide limits, substantially as and for the purpose herein set forth.

WM s. HUDSON.

Witnesses:

THOMAS D. STETsoN, KIMBALL W. STE'rsoN. 

